A microphone array is a group of two or more microphones arranged in a specific geometric configuration and used to gather and process acoustic signals. One advantage of using a microphone array over a single microphone lies in the fact that the array adds dimensional information to the signal acquisition process. Accordingly, beam forming techniques may be used to provide a main lobe for receiving signals of interest that arrive from one or more desired directions. Beam forming increases the gain of the microphone array in one or more desired directions, while decreasing the gain in other directions to thereby improve the signal-to-noise ratio of a desired signal. Beam forming techniques may also be used to reduce or nearly eliminate (null out) signals from sources in a specific direction.
Adaptive microphone arrays may be configured to reduce side interference from sources of acoustic energy that are not situated in the main lobe of the array. Temporal and spatial information included in the signals collected by the microphone array are estimated using array signal processing and adaptation procedures to formulate a filter transfer function for the array. However, these arrays have the undesirable property of degrading signals of interest in the main lobe of the array. This degradation is caused by speech leakage affecting the adaptation procedure executed by the array, as well as artifacts caused by the calculated transfer function for a specific source and array configuration, modeled by the adaptive filter.